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The parasitic fly that attacks warm-blooded animals was eliminated from the United States in the 1960s, but it’s creeping toward the Texas-Mexico border.
July 28, 2025, 5:01 a.m. ET
First came bird flu, which led to the culling of large swaths of the nation’s poultry flocks and the soaring egg prices that helped undermine President Joseph R. Biden Jr.’s re-election. Now, ranchers in Texas and officials at the Agriculture Department are raising the next alarm: the New World screwworm.
Texas livestock producers and ranchers fear the United States is ill-equipped to handle a potential outbreak of screwworm, whose incursion into the country appears increasingly likely. With beef prices already soaring, the screwworm, whose Latin name roughly translates to “man-eater,” is a real threat, to both cows and the cost of living for America’s meat lovers.
“If we wait, we lose,” Stephen Diebel, vice president of the Texas and Southwestern Cattle Raisers Association, told state lawmakers during a hearing in Austin this week as he pleaded for intervention.
The screwworm, like the measles, may have been forgotten by many, but it’s not new. And like the measles, which has cropped up in Texas recently, screwworm was once all but eradicated from the United States.
Infestations occur when a female fly lays eggs, between 10 and 400 at a time, on a fresh animal wound. Within a few hours, the eggs hatch into larvae that burrow and feed on the flesh. As the wound worsens, it attracts more flies, which lay more eggs. After about a week, adult screwworm flies can reproduce and begin the cycle all over again. The parasitic infection can kill a cow within two weeks if left untreated. There is currently no approved treatment.
“It’s like something out of a horror movie,” the Texas agriculture commissioner, Sid Miller, said in an interview. He saw distressed cattle infested with screwworm when he was a child in the early 1960s before it was nearly eradicated. “It’s quite a putrid sight,” he said.
